HITTING THE MARK, ETC. 
13 
This state of things renders long range accurately striking 
artillery of the utmost consequence at the present time. 
DESCRIPTION OF PLATE LXVII. 
The Chronograph is actuated by a fly-wheel A. 
x is a cylinder covered with prepared paper for receiving the record made 
electrically by the beat of the clock, and the cutting the threads of the 
several screens through which the shot passes in its flight. The cylinder 
is about 12 inches long ; diameter 4". 
x a toothed wheel, gearing with m so as to allow a string CD to be slowly 
unwrapped from its drum, whilst the other end is attached to the sliding 
platform L, moving about a quarter of an inch for each revolution. 
ee' electro-magnets, dd' are frames supporting the keepers,/, //the springs 
acting against the magnetic attraction. 
On interrupting the current, by the destruction of magnetism the spring 
/ carries back the keeper, which causes the arm a to strike a blow on the 
lever b. Thus the marker m is made to depart from the uniform spiral it 
was describing. But when the current is restored, the keeper being 
attracted causes the marker m to be brought back, and so continue to trace 
the spiral as if nothing had occurred to alter its course. 
E' is connected with the clock, and its marker m' records seconds. 
E is connected with the screens, and records the passage of the shot through 
each of them in succession. 
Thus, by comparing the marks made by mm', the exact velocity of the shot 
can be calculated at all points of its course. The slide l is fixed parallel to 
E and the cylinder x by the brackets g, h. 
j is a stop to regulate the distance between wheels m and d, and Y draws 
back the wheelwork ir. The depression of the lever h raises the two 
springs s, which, acting as levers, bring the diamond points of the 
markers mm' down upon the paper. 
When an experiment is to be made, the fly-wheel A is set in motion by 
hand, so as to revolve about three times in two seconds ; the currents are 
completed, the markers mm' are brought down to the paper cylinder x and 
.after four or five beats of the clock the “ signal to fire ” is given, so that in 
about ten seconds the experiment is completed and the instrument is ready 
for another. 
The passage of the balls through the fifteen screens is distinctly recog- 
nised by the ear, a peculiar tr-r-r-r-rap being heard before the sound of the 
explosion, if several hundred yards away. 
